I am an independent consultant preparing a customer training for PCI Express. Special emphasis is on MSI/MSI-X. I have purchased the Mindtree training where it is mentioned that QPI packets are either with or without payload. If theey have a payload it is always sixty-four bytes (cache-line)
Today I finally got my copy of "Weaving high-performance Multiprocessor Fabrics" and here the statement doesn't seem as clear cut. I read
- p 118, Message Class NCB has payload
- p 120, Interrupts are of class NCB and further ".... these messages carry data fields up to and including a full 64 bytes"
Does anybody here know the real story? What does a PCIe MSI(-X) message look like when it hits the destination QPI. Payload (Y/N), if Y what size